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Showing papers on "Allelopathy published in 2008"


Journal ArticleDOI
TL;DR: This work strongly proposes allelopathy as an important mechanism in the interaction between submerged macrophytes and phytoplankton in shallow lakes based on the frequent occurrence of active species and the knowledge of potential target species.

285 citations


Journal ArticleDOI
TL;DR: Under cultural eutrophication, altered nutrient (N, P) ratios and limiting nutrient supplies can stimulate increased production of allelochemicals, including toxins, by some algal species and accentuate the adverse effects of these substances on other algae.

228 citations


Journal ArticleDOI
TL;DR: Seven competing native European plant species were more competitive against the invasive species in soils with activated carbon than without, supporting the allelopathy hypothesis and suggesting lower investment of invasive plants into secondary compounds, possibly because of a higher susceptibility of plant competitors in the invasive range to these substances.
Abstract: 1. One mechanism explaining the success of invasive weeds may be the production and release of allelopathic compounds by the invader that, due to a lack of co-evolutionary history, have harmful effects on plant neighbours in the introduced range. 2. We partially tested this hypothesis by growing seven competing native European plant species either with the introduced Solidago canadensis s.l., one of the most successful invasive plants in Europe or on soil pre-cultivated with S. canadensis. We added activated carbon to the soil to neutralize organic chemical compounds with putative allelopathic effects. Furthermore, we added unsterilized soil inocula from the introduced (Switzerland) or native (USA) range to the soil to test potential confounding effects of soil microbes on invasion success. Untreated sterilized soil served as control. 3. Five out of the seven native species were more competitive against the invasive species in soils with activated carbon than without, supporting the allelopathy hypothesis. However, competitive outcomes were also influenced by the two sources of soil inoculum and by interactive effects of soil inoculum and Solidago origin suggesting that soil microbes alter allelopathic effects. 4. Achillea millefolium, the species least affected by the presence of S. canadensis and with no response to the activated carbon treatment is the only species used in this experiment reported to grow within Solidago stands in Europe, whereas the other European species tested tend to grow at the periphery of invasive Solidago stands. 5. Chemical analysis by LC-MS of Solidago root extracts revealed four main secondary chemical compounds with potential allelopathic effects. Root exudates of Solidago showed a significant inhibitory effect on growth of the model plant species Arabidopsis thaliana. The magnitude of inhibition increased with increasing concentration of the extract. 6. Synthesis. Levels of the four compounds were lower in Solidago populations from the invasive range than in populations of the same ploidy level from the native range. This suggests lower investment of invasive plants into these secondary compounds, possibly because of a higher susceptibility of plant competitors in the invasive range to these substances.

203 citations


Journal ArticleDOI
TL;DR: It was shown that adding activated carbon to potting media affected nutrient availability and plant growth, and for most species tested, activated carbon increased plant biomass, even in the absence of the potentially allelopathic agent.
Abstract: Summary • Allelopathy can play an important role in structuring plant communities, but allelopathic effects are often difficult to detect because many methods used to test for allelopathy can be confounded by experimental artifacts. The use of activated carbon, a technique for neutralizing allelopathic compounds, is now employed in tests for allelopathy; however, this technique also could produce large experimental artifacts.  In three independent experiments, it was shown that adding activated carbon to potting media affected nutrient availability and plant growth. For most species tested, activated carbon increased plant biomass, even in the absence of the potentially allelopathic agent.  The increased growth corresponded to increased plant nitrogen content, likely resulting from greater nitrogen availability. Activated carbon also affected nitrogen and other nutrient concentrations in soil media in the absence of plants.  The observed effects of activated carbon on plant growth can confound its use to test for allelopathy. The detection of allelopathy relies on the difference between plant growth in medium with carbon and that in medium without carbon in the presence of the potentially allelopathic competitor; however, this difference may be biased if activated carbon alters soil nutrient availability and plant growth even in the absence of the focal allelopathic agent.

158 citations


Journal ArticleDOI
TL;DR: Leaves of L. maackii contain phenolic compounds, including apigenin and chlorogenic acid, capable of having biological effects on other plants and insects, and these compounds were inhibitory to seed germination of Arabidopsis thaliana.
Abstract: Lonicera maackii is an invasive shrub in North America for which allelopathic effects toward other plants or herbivores have been suspected. We characterized the major phenolic metabolites present in methanol extracts of L. maackii leaves. In addition, we examined the effects of methanol–water extracts of L. maackii leaves on seed germination of a target plant species and on feeding preference and growth rate of a generalist insect herbivore. A total of 13 individual major and minor compounds were detected in crude leaf extracts by high-performance liquid chromatography coupled to electronspray ionization-tandem mass spectrometry (ESI-MS/MS). Extracts were dominated by two major flavones, apigenin and luteolin, and their glucoside derivatives, apigenin-7-glucoside and luteolin-7-glucoside. Quantities of these compounds, along with chlorogenic acid, varied between two sampling points. Leaf extracts that contained these compounds were inhibitory to seed germination of Arabidopsis thaliana. In addition, treatment of artificial diet with leaf extracts deterred feeding of the generalist herbivore, Spodoptera exigua, in choice experiments but had no effect on growth rate in short-term no-choice bioassays. Purified apigenin tended to deter feeding by S. exigua and inhibited seed germination of A. thaliana. We conclude that leaves of L. maackii contain phenolic compounds, including apigenin and chlorogenic acid, capable of having biological effects on other plants and insects.

158 citations


BookDOI
01 Jan 2008
TL;DR: The application of lelopathy in agriculture and forestry is discussed in this article, where it is used to promote rhizobacteria and mycorrhizal fungi in sustainable agriculture and Forestry.
Abstract: History.- Historical Examples of Allelopathy and Ethnobotany from the Mediterranean Region.- Allelopathy: Advances, Challenges and Opportunities.- Allelopathy in Chinese Ancient and Modern Agriculture.- Allelochemicals and Allelopathic Mechanisms.- Allelochemicals in Plants.- Allelopathy: Full Circle from Phytotoxicity to Mechanisms of Resistance.- Allelopathic Mechanisms and Experimental Methodology.- Indirect Effects of Phenolics on Plant Performance by Altering Nitrogen Cycling: Another Mechanism of Plant-Plant Negative Interactions.- Genomic Approaches to Understanding Allelochemical Effects on Plants.- Allelopathy from a Mathematical Modeling Perspective.- Application of Allelopathy in Agriculture and Forestry.- Progress and Prospect of Rice Allelopathy Research.- Rice Allelopathy Research in China.- Recent Advances in Wheat Allelopathy.- Sorghum Allelopathy for Weed Management in Wheat.- Allelochemicals in Pre-cowing Soils of Continuous Soybean Cropping and Their Autointoxication.- Autotoxicity in Agriculture and Forestry.- Black Walnut Allelopathy: Implications for Intercropping.- Plant Growth Promoting Rhizobacteria and Mycorrhizal Fungi in Sustainable Agriculture and Forestry.- Utilization of Stress Tolerant, Weed Suppressive Groundcovers for Low Maintenance Landscape Settings.- Allelopathy in Forested Ecosystems.

157 citations


Journal ArticleDOI
TL;DR: The results indicate that allelopathy is an important mechanism to take into account when trying to understand the causes and consequences of plant invasions, and strongly suggests that the real significance of the allelopathic effects of an invasive species cannot be assessed independently of its target community, or in isolation of other resource interactions involving the invader and the native community.
Abstract: Summary 1. Allelopathic interactions between invasive and native species have been suggested to be an important mechanism for the success of some of the most aggressive plant invaders. However, field experiments that test the effects of natural levels of allelopathic compounds on coexisting native species are exceptionally rare. 2. In this study, we analyzed the allelopathic effects of the invasive tree Ailanthus altissima on seedling emergence, survival and growth of three native tree species ( Acer rubrum , A. saccharum and Quercus rubra ) in temperate forests of the northeastern United States. We used activated carbon (AC) to reduce potential allelopathic interference, and developed neighbourhood models that explain the observed spatial variation in the effects of the AC treatments on seedling performance as a function of the size, abundance and distribution of Ailanthus trees in the neighbourhood. 3. Our results showed that the addition of AC to the soil did not affect seedling emergence or survival, but caused a significant increase in seedling growth of all three species. Moreover, the AC shifted the overall interaction between Ailanthus and maple seedlings from neutral or slightly positive to very positive for A. rubrum, and from negative to positive for A. saccharum , whereas the net interaction between Ailanthus and Q. rubra was always negative. As Ailanthus has the ability to increase soil fertility, these species-specific responses are presumably influenced by among-species differences in the net effects of both allelopathy and changes in resource availability caused by the presence of Ailanthus . 4. The cumulative allelopathic effects of Ailanthus were proportional to the density of Ailanthus in the neighbourhood, regardless of their size. In contrast, Ailanthus effects were strongly influenced by distance from a tree, generally dropping to zero within 5 m from the trunk. 5. Synthesis. Taken together, our results indicate that allelopathy is an important mechanism to take into account when trying to understand the causes and consequences of plant invasions. However, this study also strongly suggests that the real significance of the allelopathic effects of an invasive species cannot be assessed independently of its target community, or in isolation of other resource interactions involving the invader and the native community.

146 citations


Journal ArticleDOI
TL;DR: It is shown that allelopathic rice can have great impact on the population and community structure of soil microbes, and variation in soil microbial populations and community structures could be distinguished by the allelopathy and non-allelopathic rice varieties tested.
Abstract: Allelopathic rice releases allelochemicals from its roots to paddy soils at early growth stages to inhibit neighboring weeds. However, little is currently known about the effects of allelochemicals on soil microbes. In this study, we show that allelopathic rice can have great impact on the population and community structure of soil microbes. Allelopathic rice P1312777 seedlings reduced the culturable microbial population and total PLFA when compared to non-allelopathic rice Liaojing-9. Similar results were observed when, instead of growing seedlings, soils were incubated with plant root exudates. This result demonstrates that the composition of root exudates from the rice varieties tested contributes to the soil microbial community. Further experiments showed that the microbial community was affected by the allelochemical 5,4'-dihydroxy-3',5'-dimethoxy-7-O-beta-glucopyranosylflavone exuded from allelopathic rice roots, through immediately hydrolyzing glucose with stimulation on soil bacteria and aglycone (5,7,4'-trihydroxy-3',5'-dimethoxyflavone) with inhibition on soil fungi. This result indicates that the flavone O-glycoside can provide carbon and interact with soil microbes. PC analysis of the fatty acid data clearly separated the allelopathic P1312777 and the non-allelopathic Liaojing-9 variety (PC1 = 46.4%, PC2 = 20.3%). Similarly, the first principal component (PC1 = 37.4%) together with the second principal component (PC2 = 17.3%) explained 54.7% of the variation between the allelopathic and non-allelopathic root exudates. Furthermore, the canonical correlation between allelopathic root exudates and the flavone O-glycoside was statistically significant (Canonical R = 0.889, chi(2) (25) = 69.72, p = 0.0041). Although the data generated in this study were not completely consistent between culturable microbes and PLFA profile, it is a fact that variation in soil microbial populations and community structures could be distinguished by the allelopathic and non-allelopathic rice varieties tested. Our results suggest that individual components of rice root exudates, such as allelochemicals from allelopathic rice, can modify the soil microbial community. (C) 2008 Elsevier Ltd. All rights reserved.

113 citations


Journal ArticleDOI
TL;DR: The understanding of the allelochemical action mechanisms allow us to use these compounds to enhance crop production and develop a more sustainable agriculture, including weed and pest control through crop rotations, residue management and a variety of approaches in biocontrol.

109 citations


Journal ArticleDOI
TL;DR: An understanding of persistence, fate and phytotoxicity of allelochemicals in the natural environment is developed, and the possible solution of the problems due to microbial interventions in the soil is pointed out.
Abstract: Soil microorganisms interact with plants in diversified manner ranging from mobilising nutrients and enhancing their growth, to inducing diseases. They also produce allelochemicals directly or indirectly through conversion from other compounds. In order to hamper plant growth, allelochemicals must accumulate and persist at phytotoxic levels in the rhizosphere soil. However, after their entry into environment, persistence, availability and biological activities of allelochemicals are influenced by microorganisms. Transformation of allelochemicals by soil microbes may result into the compounds with modified biological properties. Such bio-transformations affect the overall allelopathic capability of the producer plant in a direct manner. Several reports describe the allelopathic significance of microbial metabolism products. For instance, a bacteriumActinetobacter calcoaceticus, can convert 2 (3H)-benzoxazolinone (BOA) to 2,2′-oxo-l,l′-azobenzene (AZOB) which is more inhibitory to some plants. On the contrary, bacteriumPseudomonas putida catabolises juglone in soils beneath walnut trees; otherwise, juglone accumulates at phytotoxic levels. This review article describes the nature of microbially produced allelochemicals, and the ways to mediate microbial degradation of putative allelochemicals. The given information develops an understanding of persistence, fate and phytotoxicity of allelochemicals in the natural environment, and also points out the possible solution of the problems due to microbial interventions in the soil.

97 citations


Journal ArticleDOI
TL;DR: Allelopathy, including inhibition or stimulation of growth, was assessed by cocultivation of each of the isolated strains, as well as by evaluation of extracts prepared from the isolates, and the most pronounced activity was observed for the cyanobacterial isolate Fischerella sp.

Journal ArticleDOI
TL;DR: Testing the hypotheses that allelopathic effects of the endophyte reduce AM fungal spore germination and the allelochemical compound(s) are leached into the soil even after the death of S. phoenix observed situations whereby two ecologically widespread plant-microbe symbioses interact.
Abstract: Summary 1. Plants can host microbial communities whose integrated functions are often responsible for their success. Understanding mechanisms regulating such functions is thus a major goal in ecology. 2. Fungal endophytes of grasses, particularly of the genus Neotyphodium , have been reported to reduce colonization of their host plant by arbuscular mycorrhizal (AM) fungi. However, it is unclear which mechanism(s) may explain the effects produced by the endophyte and whether these effects are present in nature. 3. We used Schedonorus phoenix (syn. Lolium arundinaceum ) plants that were endophyte-free or infected with one of two strains of Neotyphodium coenophialum known to produce different putative allelochemicals to test the hypotheses that (i) allelopathic effects of the endophyte reduce AM fungal spore germination; and (ii) the allelochemical compound(s) are leached into the soil even after the death of S. phoenix , where they reduce AM fungal colonization of other plants. 4. In a first experiment, aqueous extracts from the shoots of S. phoenix were applied onto spores of the AM fungus Glomus intraradices to test germination effects. Both endophyte strains reduced spore germination by approximately 10% relative to endophyte-free controls. 5. In a second experiment, we placed dried shoot material (‘thatch’) on the soil surface of pots containing Bromus inermis , which were either inoculated with G. intraradices or not. We watered the plants through the thatch, relying upon leaching to translocate potential allelochemicals to the soil. AM fungal colonization of B. inermis was significantly reduced when thatch was infected with the common strain, but not with AR542, compared to the endophyte-free thatch. Furthermore, the arbuscule : vesicle ratio was 11-fold smaller when thatch was infected with the common strain compared to endophyte-free thatch, suggesting that G. intraradices was stressed by the presence of common strain-leachate. 6. We observed situations whereby two ecologically widespread plant-microbe symbioses interact. Potential mechanisms may include allelopathic effects, although other factors are also possible, and leaching is a mode of entry of putative endophyte-induced AM fungal inhibitors in soil. Understanding these processes is important as they affect AM fungal communities which contribute to plant success and, consequentially, grassland ecosystem dynamics.

Journal ArticleDOI
TL;DR: The aim of this study was to look for evidence of a llelochemicals in B. decumbens, in parts of the plant from where they could easily be released to the environment, and to assess the effectiveness of the aqueous leachates in reducing germination of species tested.
Abstract: The aim of this study was to look for evidence of a llelochemicals in B. decumbens , in parts of the plant from where they could easily be released to the environment. T he germination inhibition of Phalaris canariensis , Lactuca sativa (standard species) and Melinis minutiflora , another invasive African grass, was tested using B. decumbens germinating seeds and aqueous leachates of the roo ts, green and senescent leaves, at 5, 10 and 20% w/ v. Both the germinating seeds and the aqueous leachates of B. decumbens reduced the germination of the species tested; the effectiveness of the aqueous leachates increased ac cording to concentration. Apparently, the competiti ve advantage of B. decumbens in the cerrados could be amplified via allelopathy .

Journal ArticleDOI
TL;DR: In this paper, the development and potential application about allelopathy of aquatic plants on algae, including the allelopathic research history, the potential research problems, the research methodology, and the reported aquatic macrophytes and their inhibitory allelochemicals were also presented.
Abstract: Algal-bloom control is an important issue for water environment protection as it induces several negative impacts on the lives of aquatic organisms, aquaculture, landscaping, and human health. The development of an environment-friendly, cost-effective, and convenient alternative for controlling algal bloom has gained much concern. Using the allelopathy of aquatic macrophytes as a novel and safe method for algal-bloom control is a promising alternative. This paper reviews the development and potential application about allelopathy of aquatic plants on algae, including the allelopathic research history, the potential research problems, the research methodology, and the reported aquatic macrophytes and their inhibitory allelochemicals. Potential modes of inhibition action of allelochemicals on algae, possible ways for application, and future development directions of research on algal-bloom control by aquatic macrophytes were also presented.

Journal ArticleDOI
TL;DR: It is shown that autotoxicity is a potential functional process that could influence natural regeneration of P. halepensis, but field conditions studies are necessary.

Journal ArticleDOI
TL;DR: The data indicate that allelochemicals might have relevant functions, at least in part, in the cross-talk between biotic and abiotic stress signalling because they generate ROS, which has been proposed as a key shared process between these two stress mechanisms.
Abstract: Buckwheat (Fagopyrum esculentum Moench) is an important annual plant cultivated for grain or as a cover crop in many countries, and it is also used for weed suppression in agro-economic systems through its release of allelochemicals Little is known, however, concerning the mode of action of allelochemicals or plant defence response against them Here, microarrays revealed 94, 85, and 28 genes with significantly higher expression after 6 h of exposure to the allelochemicals fagomine, gallic acid, and rutin, respectively, compared with controls These induced genes fell into different functional categories, mainly: interaction with the environment; subcellular localization; protein with binding function or cofactor requirement; cell rescue; defence and virulence; and metabolism Consistent with these results, plant response to allelochemicals was similar to that for pathogens (biotic stress) or herbicides (abiotic stress), which increase the concentration of reactive oxygen species (ROS; with consequent oxidative stress) in plant cells The data indicate that allelochemicals might have relevant functions, at least in part, in the cross-talk between biotic and abiotic stress signalling because they generate ROS, which has been proposed as a key shared process between these two stress mechanisms

Journal ArticleDOI
TL;DR: The content of 2,4-dihydroxy-1,4 (2H)-benzoxazin-3-one (DIBOA) and benzoxazolin-2(3H)-one (BOA), indicated as benzoxzinoids and considered effective for weed control, and the ability of mulches to inhibit the germination of four warm-season weeds are studied.
Abstract: In conventional agriculture, weed control by herbicides is an expensive practice and can also have a negative effect on the environment. Allelopathy permits sustainable weed management while reducing the impact of agriculture on the environment. We studied the content of 2,4-dihydroxy-1,4 (2H)-benzoxazin-3-one (DIBOA) and benzoxazolin-2(3H)-one (BOA), indicated as benzoxazinoids and considered effective for weed control, in 8 cultivars of rye and 1 of triticale grown in a greenhouse. We also tested the ability of mulches to inhibit the germination of four warm-season weeds. Our results show that all rye cultivars produced DIBOA, while BOA was found only in four of them. Benzoxazinoids were absent in triticale. Total benzoxazinoid content ranged from 177 to 545 μg g−1 and was statistically different among cultivars. Rye mulches were not able to suppress velvetleaf and common lambsquarters seedlings, while redroot pigweed and common purslane were significantly affected. Weed suppression ranged from 40% to 52% for redroot pigweed and from 40% to 74% for common purslane. The inhibitory activity of triticale mulch was observed only for common purslane, with a suppression percentage of 33%. No correlation was found between total benzoxazinoid content and the number of weed seedlings suppressed, with R2 of 0.076 for redroot pigweed and R2 of 0.003 for common purslane, indicating that benzoxazinoids are not the only source of phytotoxicity.

Journal ArticleDOI
02 Jul 2008-PLOS ONE
TL;DR: It is demonstrated that (±)-catechin is highly dynamic in natural soils, but is phytotoxic well below natural concentrations measured in some soils and applied at low concentrations in the field, and there is substantial conditionality in the effects of the allelochemical.
Abstract: BACKGROUND Exploring the residence time of allelochemicals released by plants into different soils, episodic exposure of plants to allelochemicals, and the effects of allelochemicals in the field has the potential to improve our understanding of interactions among plants. METHODOLOGY/PRINCIPAL FINDINGS We conducted experiments in India and the USA to understand the dynamics of soil concentrations and phytotoxicity of (+/-)-catechin, an allelopathic compound exuded from the roots of Centaurea maculosa, to other plants in vitro and in soil. Experiments with single and pulsed applications into soil were conducted in the field. Experimental application of (+/-)-catechin to soils always resulted in concentrations that were far lower than the amounts added but within the range of reported natural soil concentrations. Pulses replenished (+/-)-catechin levels in soils, but consistently at concentrations much lower than were applied, and even pulsed concentrations declined rapidly. Different natural soils varied substantially in the retention of (+/-)-catechin after application but consistent rapid decreases in concentrations over time suggested that applied experimental concentrations may overestimate concentrations necessary for phytotoxicity by over an order of magnitude. (+/-)-Catechin was not phytotoxic to Bambusa arundinacea in natural Indian soil in a single pulse, but soil concentrations at the time of planting seeds were either undetectable or very low. However, a single dose of (+/-)-catechin suppressed the growth of bamboo in sand, in soil mixed with organic matter, and Koeleria macrantha in soils from Montana and Romania, and in field applications at 40 microg l(-1). Multiple pulses of (+/-)-catechin were inhibitory at very low concentrations in Indian soil. CONCLUSIONS/SIGNIFICANCE Our results demonstrate that (+/-)-catechin is highly dynamic in natural soils, but is phytotoxic well below natural concentrations measured in some soils and applied at low concentrations in the field. However, there is substantial conditionality in the effects of the allelochemical.

Journal ArticleDOI
TL;DR: This study showed that L. peploides and L. grandiflora possess an allelopathic activity that influences the water quality throughout the year and may contribute to the great success of these two invasive Ludwigia in Europe.

Journal ArticleDOI
TL;DR: It was found that while both the dry weight root and stems elongation of muskmelon and cucumber seedlings were affected negatively by juglone and undiluted decomposed walnut leaf juices, the negative effect decreased as dilution ratios of decomposed leaf juice increased.
Abstract: In this study, effects of juglone and decomposed walnut leaf juice on muskmelon (Cucumis melo cv. Galia) and cucumber (Cucumis sativus cv. Beith Alpha) seed germination percentage and postgermination seedling growth were investigated. Decomposition was carried out by keeping the leaves in distilled water. Muskmelon and cucumber seeds were germinated in Petri dishes at 25°C. Seed germination, seedling elongation and weights were determined at day 10. No significant effect of juglone and decomposed walnut leaf juice on muskmelon seed germination percentage was observed. However, germination of cucumber seed was inhibited significantly. It was found that while both the dry weight root and stems elongation of muskmelon and cucumber seedlings were affected negatively by juglone and undiluted decomposed walnut leaf juices. The negative effect decreased as dilution ratios of decomposed leaf juice increased.

Journal ArticleDOI
TL;DR: While nutrient addition substantially improved the performance of Arabidopsis thaliana grown in field soils in pots in a growth room, addition of A. petiolata extracts to these soils had no significant independent or interactive effects on growth or reproduction, which revealed that effects of L. maackii were independent of allelopathic effects on mycorrhizae.
Abstract: In addition to resource competition, allelopathy is believed to contribute to the invasiveness and impact of several plant invaders of North America. In this study, we examined whether aqueous leaf extracts of Alliaria petiolata and Lonicera maackii, two invaders of deciduous forests in North America, affected growth and reproduction of a target nonmycorrhizal plant and whether effects varied across a soil fertility gradient. While nutrient addition substantially improved the performance of Arabidopsis thaliana grown in field soils in pots in a growth room, addition of A. petiolata extracts to these soils had no significant independent or interactive effects on growth or reproduction. In contrast, addition of L. maackii extracts both directly reduced growth and reproduction of A. thaliana and greatly constrained increases in growth and reproduction of A. thaliana in response to increasing nutrient availability. Use of a nonmycorrhizal target plant revealed that effects of L. maackii were independent of al...

Journal ArticleDOI
Chun-mei Han1, Kaiwen Pan1, Ning Wu1, Jinchuang Wang1, Wei Li1 
TL;DR: It is suggested that ginger allelochemicals are heterotoxic, and thus intercropping should not be practiced using ginger, and the residue of the ginger plant should be removed from the field so as to diminish its inhibitory effect.

Journal ArticleDOI
TL;DR: A relationship between allelopathy, biosynthesis, catabolism and terpene release is proposed for the chemical ecological effect of T. minuta.

Journal ArticleDOI
TL;DR: The ecological importance of the different effects of crushed and intact fruits is supported by field observations which found equal or greater numbers of crushed fruits compared to intact fruits beneath the tree canopy of female S. terebinthifolius.

Journal ArticleDOI
TL;DR: The results suggest that competitors differ in their responses to phytoplankton allelopathy, with S. costatum exhibiting a previously undescribed method of resistance that may influence community structure and alter bloom dynamics.
Abstract: Biotic interactions in the plankton can be both complex and dynamic. Competition among phytoplankton is often chemically mediated, but no studies have considered whether allelopathic compounds are modified by biotic interactions. Here, we show that compounds exuded during Karenia brevis blooms were allelopathic to the cosmopolitan diatom Skeletonema costatum, but that bloom allelopathy varied dramatically among collections and years. We investigated several possible causes of this variability and found that neither bloom density nor concentrations of water-borne brevetoxins correlated with allelopathic potency. However, when we directly tested whether the presence of competing phytoplankton influenced bloom allelopathy, we found that S. costatum reduced the growth-inhibiting effects of bloom exudates, suggesting that S. costatum has a mechanism for undermining K. brevis allelopathy. Additional laboratory experiments indicated that inducible changes to K. brevis allelopathy were restricted to two diatoms among five sensitive phytoplankton species, whereas five other species were constitutively resistant to K. brevis allelopathy. Our results suggest that competitors differ in their responses to phytoplankton allelopathy, with S. costatum exhibiting a previously undescribed method of resistance that may influence community structure and alter bloom dynamics.

Journal ArticleDOI
TL;DR: It is feasible to reduce herbicide input in paddies if allelopathic rice is grown under integrated cultural management practices, and the allelopathy potential of rice varieties will likely have a great impact on paddy weed control if integrated with cultural management options and application of low doses of herbicides.
Abstract: BACKGROUND: A number of techniques, including cultural management, allelopathy and bioherbicide, have been considered as alternatives for synthetic herbicides, but successful weed control will require the careful integration of these multiple techniques. This study was conducted to assess the use of allelopathic rice varieties in combination with cultural management options on paddy weeds, in order to develop an allelopathy-based technique to reduce herbicide use in paddies. RESULTS: The weed-suppressive effects of the rice varieties tested varied highly with allelopathic trait, planting pattern and cultural management including planting density, flooding depth and duration and supply of nitrogen. Allelopathic rice varieties PI312777 and Huagan-1 demonstrated much stronger weed suppression than the non-allelopathic variety Huajianxian under the same planting pattern and cultural management. Their weed-suppressive effect was increased with cultural management options. In particular, if integrated cultural management options of allelopathic rice varieties included a low-dose (bensulfuron-methyl, 25 g AI ha(-1) a third of the recommended dose) herbicide application, the emergence and growth of most weeds found in paddy fields was completely controlled. No grain yield reduction for allelopathic varieties occurred under integrated cultural management options, whereas with the non-allelopathic variety a reduction of up to 45-60% was measurable even with the low-dose herbicide application. CONCLUSION: The allelopathic potential of rice varieties will likely have a great impact on paddy weed control if integrated with cultural management options and application of low doses of herbicides. Therefore, it is feasible to reduce herbicide input in paddies if allelopathic rice is grown under integrated cultural management practices. (c) 2008 Society of Chemical Industry.

Journal ArticleDOI
TL;DR: It is shown that the leaf oil emulsion of E. grandis × E. urophylla can inhibit the proliferation of pathogenic fungi Fusarium oxysporum, Pyriculerie grisea, Glorosprium musa rum and Phytophthora capsici.
Abstract: This study on the allelopathic effects and chemical components of the essential oi l from Eucalyptus grandis × E. urophylla shows that the leaf oil emulsion of E. grandis × E. urophylla can inhibit the proliferation of pathogenic fungi Fusarium oxysporum, Pyriculerie grisea, Glorosprium musa rum and Phytophthora capsici. Pupation and feeding of the pest insects Spodopteralitura Fabricius and Helicoverpa armigera Hubner are shown to be affected with restraining effects which increase with the increasing levels of oil concentration. A GC/MS analysis of the leaf oil indicated that the main components, with a relative content of ⩾3%, were alloocimene (43.22%), α-pinene (13.63%), γ-terpinene (5.49%), (E)-3,7-dimethyl-2,6-octadien-1-ol (3.58%), β-fenchyl alcohol (4.58%), and 2-amino-3,5-dicyano-6-(4-methoxyphenoxy)-pyridine (3.67%). Terpenes played an important role in the inhibitory effects of E. grandis × E. urophylla essential oil on pathogenic fungi and pest insects. Poor biodiversity of eucalyptus plantations is a function of allelopathy.

Book ChapterDOI
T. Haig1
01 Jan 2008
TL;DR: This chapter presents a brief coverage of a range of common plant allelochemical groups, and includes discussion of their structures, chemistry, distribution, ecology, bioactivity, biosynthesis, allelopathy, and mode of action where known.
Abstract: This chapter presents a brief coverage of a range of common plant allelochemical groups, and includes discussion of their structures, chemistry, distribution, ecology, bioactivity, biosynthesis, allelopathy, and mode of action where known.

Journal ArticleDOI
Chui-Hua Kong1, Pucai Wang1, Gu Yongwei1, Xiushang Xu1, Mei Wang1 
TL;DR: It appeared from the results that flavone could reduce microorganisms especially for fungi present in paddy soil, while benzoic acid could induce a higher response for soil micro organisms especially for bacteria.
Abstract: Allelopathic rice can release allelochemicals from roots to inhibit neighboring plant species, but little is currently known about their fate and impact on microorganisms in paddy soil. This study showed that allelopathic rice P1312777 released much higher concentrations of allelochemical (5,7,4'-trihydroxy-3',5'-dimethoxyflavone) than non-allelopathic rice Liaojing-9 in field. When quantitative 5,7,4'-trihydroxy3',5'-dimethoxyflavone was added into soil, flavone gave a short half-life of 18.27 +/- 2.32 h (r(2) = 0.94) and could easily be degraded into benzoic acid. Benzoic acid with a half-life of 29.99 +/- 2.19 h (r(2) = 0.96) was more resistant toward degradation in paddy soil. Furthermore, both the culturable microbial population and the entire microbial community structure of soil incubated with flavone and benzoic acid were evaluated using the soil dilution plate method and phospholipid fatty acid (PLFA) analysis, respectively. It appeared from the results that flavone could reduce microorganisms especially for fungi present in paddy soil, while benzoic acid could induce a higher response for soil microorganisms especially for bacteria. Consequently, flavone would be responsible for the dynamics of soil microorganisms during the early period, and any observed effect during the late period would be very likely due to its degradation product. benzoic acid rather than flavone itself. These results suggested that allelopathic rice varieties could modify soil microorganisms to their advantage through the release of allelochemicals. The concentration and fate of discriminating 5,7,4'-trihydroxy-3',5'-dimethoxyflavone between allelopathic and non-alleloparhic varieties tested in rice soil would result in the different patterns of microbial population and community structure in paddy ecosystems.

Journal ArticleDOI
TL;DR: The use of essential oils can be applied for biological control of weeds as pre-emergent weed seed germination inhibitors and, they can decrease the use of chemical herbicides.
Abstract: A study was conducted to assess the allelopathic effects of essential oils from Eucalypt, Lawson Cypress, Rosemary and White cedar with the objective of exploring the possibility of their utilization for future weed management. The effects of these four essential oils on the germination of three weed species were examined. The essential oils severely affected the germination percentage of the weed species and showed allelopathic potential. The results demonstrated that germination of the weed species was strongly inhibited by all essential oils, especially Eucalypt oil, when applied at 300 ppm. Results showed that the use of essential oils can be applied for biological control of weeds as pre-emergent weed seed germination inhibitors and, they can decrease the use of chemical herbicides. The possible use of essential oils as herbicides is discussed.